Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Balance at March 31, 2021 at Dec. 31, 2019	$ 891,957,000	$ 442,000	$ 280,216,000	$ 645,507,000	$ (24,829,000)	$ (9,379,000)
Balance (in shares) at Dec. 31, 2019		44,209
Increase (Decrease) in Stockholders' Equity
Net income	90,305,000			90,305,000
Translation adjustment	(3,069,000)				(3,069,000)
Translation adjustment, net of tax	61,000				61,000
Unrealized gains (losses) on derivative instruments	0
Stock-based compensation	4,830,000		4,830,000
Shares issued from release of Restricted Stock Units	(7,741,000)	$ 2,000	(7,743,000)
Shares issued from release of Restricted Stock Units (in shares)		162
Repurchase of common stock	(62,679,000)					(62,679,000)
Repurchase of common stock (in shares)		(902)
Dividends, Common Stock, Cash	(19,774,000)			(19,774,000)
Common stock issued	322,000		322,000
Common stock issued (in shares)		4
Balance at Jun. 30, 2020	894,212,000	$ 444,000	277,625,000	716,038,000	(27,837,000)	(72,058,000)
Balance (in shares) at Jun. 30, 2020		43,473
Balance at March 31, 2021 at Mar. 31, 2020	841,594,000	$ 444,000	272,872,000	672,485,000	(32,149,000)	(72,058,000)
Balance (in shares) at Mar. 31, 2020		43,464
Increase (Decrease) in Stockholders' Equity
Net income	53,479,000			53,479,000
Translation adjustment	4,525,000				4,525,000
Translation adjustment, net of tax	(213,000)				(213,000)
Unrealized gains (losses) on derivative instruments	0
Stock-based compensation	4,797,000		4,797,000
Shares issued from release of Restricted Stock Units	(44,000)	$ 0	(44,000)
Shares issued from release of Restricted Stock Units (in shares)		9
Dividends, Common Stock, Cash	(9,926,000)			(9,926,000)
Balance at Jun. 30, 2020	894,212,000	$ 444,000	277,625,000	716,038,000	(27,837,000)	(72,058,000)
Balance (in shares) at Jun. 30, 2020		43,473
Balance at March 31, 2021 at Dec. 31, 2020	980,943,000	$ 433,000	284,007,000	720,441,000	(10,428,000)	(13,510,000)
Balance (in shares) at Dec. 31, 2020		43,326
Increase (Decrease) in Stockholders' Equity
Net income	122,872,000			122,872,000
Translation adjustment	(1,759,000)				(1,759,000)
Translation adjustment, net of tax	409,000				409,000
Unrealized gains (losses) on derivative instruments	19,000
Stock-based compensation	9,826,000		9,826,000
Shares issued from release of Restricted Stock Units	(5,262,000)	$ 1,000	(5,263,000)
Shares issued from release of Restricted Stock Units (in shares)		104
Common stock issued at $93.45 per share for stock bonus	1,000
Dividends, Common Stock, Cash	(20,816,000)			(20,816,000)
Common stock issued	692,000		691,000
Common stock issued (in shares)		7
Balance at Jun. 30, 2021	1,086,905,000	$ 435,000	289,261,000	822,497,000	(11,778,000)	(13,510,000)
Balance (in shares) at Jun. 30, 2021		43,437
Balance at March 31, 2021 at Mar. 31, 2021	1,014,509,000	$ 435,000	285,896,000	760,862,000	(19,174,000)	(13,510,000)
Balance (in shares) at Mar. 31, 2021		43,430
Increase (Decrease) in Stockholders' Equity
Net income	72,483,000			72,483,000
Translation adjustment	7,505,000				7,505,000
Translation adjustment, net of tax	(109,000)				(109,000)
Unrealized gains (losses) on derivative instruments	(7,000)
Stock-based compensation	3,365,000		3,365,000
Shares issued from release of Restricted Stock Units	0	$ 0	0
Shares issued from release of Restricted Stock Units (in shares)		7
Dividends, Common Stock, Cash	(10,848,000)			(10,848,000)
Balance at Jun. 30, 2021	$ 1,086,905,000	$ 435,000	$ 289,261,000	$ 822,497,000	$ (11,778,000)	$ (13,510,000)
Balance (in shares) at Jun. 30, 2021		43,437